Science Buddies: "Ask an Expert"

Hi,
I'm a junior conducting an independent research project. For my project I want to determine the Effect of Concentration of Ca²⁺ (I'll be using calcium chloride) on the Intensity of Light Given Off By Vibrio Fischeri. I know that I will have to dissolve the calcium chloride in the nutrient agar provided by CAROLINA, and spawn the bacteria on that agar. But in order to measure the light intensity of the bacteria, I need the bacteria to be living in some sort of liquid medium. I can't liquefy the agar with the bacteria in it, because this specific bacteria only lives in cold conditions, and if I heat them up they'll die. I also can't spawn my bacteria in an aqueous calcium chloride solution, because they have a need of other nutrients, that are provided in the agar. I also have expense limitations. But my school has this: https://www.vernier.com/products/sensors/ls-bta/
My physics teacher said that I'd have to somehow transfer the contents of the agar in a test tube in liquid form.
I'm kind of in a dilemma. Any ideas?
Thanks,
Shreya

Welcome to Science Buddies!

Interesting idea for a project!

My first thought is you could make some liquid media (all the nutrients in the agar plate mix but without the agar). We use this in our lab routinely, sometimes we need to grow our cultures in liquid, so we just remove the agar from the recipe for our plates.
To grow in the liquid you pick one colony off of your plate using a sterile loop. Then you would dip the loop into the liquid media in a sterile tube.

Since you want to measure the effect of Ca2+ on the intensity of light, the liquid media must contain the same concentration(s) that your plates contain.

This would allow you to culture your bacteria in a liquid. Does that help?


Extra notes that may or may not help -

The main liquid media recipe I have found is called SWT and contains:
0.5% Bacto Tryptone (Difco Co., St. Louis, Mo.), 0.3% yeast extract, and 0.3% glycerol in 70% seawater

There is also the Luria-Bertani Seawater media recipe, but it has more ingredients:
1% Bacto Tryptone, 0.5% yeast extract, 2% NaCl, and 20 mM Tris-HCl (pH 7.4)

Reference for recipes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC421587/

Bacto Tryptone, yeast extract, and glycerol should be found in any science lab and should be relatively inexpensive.

Good Luck!

-AJ